More and more electronic devices are incorporating rechargeable batteries. Telephones, radios, laptop computers, compact disc players, video games, video recorders, personal organizers, power tools, and the like all require batteries for portability. The cost of replacing single use batteries, alkaline for instance, can be prohibitive. In an effort to save consumers money, electronics manufacturers are designing products which incorporate rechargeable batteries as opposed to single use cells. As rechargeable batteries can be charged and discharged thousands of times before replacement is needed, the overall cost of operating a rechargeable device becomes much cheaper.
Adding a rechargeable battery to a device, however, is not as simple as merely connecting a rechargeable cell to a circuit. Improper charging of rechargeable cells can be detrimental to battery performance. For example, a popular battery choice in rechargeable devices is the lithium-ion cell. When lithium cells are improperly charged or discharged, they can release gasses, causing damage to the cell. This condition of gaseous release, known as "venting", typically causes battery operation to cease.
To prevent venting from occurring, protection circuits, also called "safety circuits", are connected to rechargeable cells. Protection circuits often include a switch that opens when the battery temperature gets too hot. When the switch opens, no current can flow and venting is effectively stopped.
Such protection circuits are manufactured using resistors, capacitors, transistors and the like. They are mounted to either a rigid circuit board, often called a "PC Board", or to a flexible circuit board, sometimes called a "flex". The technical term for circuit boards and flexes is "substrate".
To make a complete rechargeable battery device, the safety circuit, along with its substrate, must be connected to the battery cell. In the past, this was done by soldering a wire onto the substrate and then soldering the opposite end of the wire to the battery cell. This is a tedious process which is labor intensive, slow, and expensive.
An alternative method of attaching substrates to cells is by using thin, flat pieces of flexible metal. These "tabs" can be soldered onto the substrate and then welded onto the board. The problem with tabs is that they must be soldered to the substrate and then bent around the cell for welding. This bending process often causes the tab to tear.
There is therefore a need for an improved method of attaching a substrate to a cell.